scientific muscle
New Member
The recent thread about Chad Waterbury's confused description of motor-unit recruitment and training got me thinking and I dug up this old post of mine from the Max-stim forum.
I hope this helps some newbies understand muscle fiber recruitment and why fatigue is not the stimulus for hypertrophy. This will also explain why I like max-stim and fatigue management so much, and why I think it is the best version of HST so far....
"Each individual motor neuron controls a bundle of muscle fibers called a motor unit. The more motor units (MUs) we recruit the more tension we produce which is translated into force. When we lift max-stim style, the loads are relatively high (60%-95% of our 1rm). We also lift with full force, meaning fast reps. In a full force contraction, ALL MUs are being fired simultaneously in a state of complete tetanus. (tetanus means the MUs are firing in a rapid series, so rapid that the multiple twitches appear to be one continuous, smooth contraction.) This is full-fiber recruitment, all MUs are participating in the contraction, producing 100% of their force capability. This of course puts enormous strain on the muscle and depletes their energy reserves rapidly. These full-force contractions produce the greatest stimulus for hypertrophy. However, such contractions cannot be long sustained due to fatigue. When lifting lighter loads that do not require full-force, the MNs (motor neurons) fire on a rotating basis. (X) amount of MUs are needed to produce (Y) amount of force. Since (X) is less than the sum total of all MUs, then some MUs are resting while others are firing. They alternate 'shifts' so that each MU has a chance to rest while others are firing. In this case since only partial recruitment is occuring, it takes longer for the muscle to fatigue and thus fatigue must be first induced in the muscle before full recruitment can occur.
So when lifting your 15 rm and going to failure, full-recruitment doesn't occur until the last few reps. The last few reps seem harder because some of the MUs have already fatigued (depleted energy reserves), so full recruitment is necessary to keep lifting. When failure occurs, enough MUs are fatigued to the point that force production is too small too overcome the resistance.
HIT training gets some full-recruitment, which is good, but at the expense of heavy fatigue, which is bad for muscle contraction and recovery.
Max-Stimulation training gets full-recruitment (or very close) on each and every rep for multiple reps. The m-time between each rep allows the muscle to restore some lost energy reserves, putting off fatigue and allowing more total reps. More heavy reps = more full-force contractions, and hence maximal stimulation of the hypertrophy response."
I hope this helps some newbies understand muscle fiber recruitment and why fatigue is not the stimulus for hypertrophy. This will also explain why I like max-stim and fatigue management so much, and why I think it is the best version of HST so far....
"Each individual motor neuron controls a bundle of muscle fibers called a motor unit. The more motor units (MUs) we recruit the more tension we produce which is translated into force. When we lift max-stim style, the loads are relatively high (60%-95% of our 1rm). We also lift with full force, meaning fast reps. In a full force contraction, ALL MUs are being fired simultaneously in a state of complete tetanus. (tetanus means the MUs are firing in a rapid series, so rapid that the multiple twitches appear to be one continuous, smooth contraction.) This is full-fiber recruitment, all MUs are participating in the contraction, producing 100% of their force capability. This of course puts enormous strain on the muscle and depletes their energy reserves rapidly. These full-force contractions produce the greatest stimulus for hypertrophy. However, such contractions cannot be long sustained due to fatigue. When lifting lighter loads that do not require full-force, the MNs (motor neurons) fire on a rotating basis. (X) amount of MUs are needed to produce (Y) amount of force. Since (X) is less than the sum total of all MUs, then some MUs are resting while others are firing. They alternate 'shifts' so that each MU has a chance to rest while others are firing. In this case since only partial recruitment is occuring, it takes longer for the muscle to fatigue and thus fatigue must be first induced in the muscle before full recruitment can occur.
So when lifting your 15 rm and going to failure, full-recruitment doesn't occur until the last few reps. The last few reps seem harder because some of the MUs have already fatigued (depleted energy reserves), so full recruitment is necessary to keep lifting. When failure occurs, enough MUs are fatigued to the point that force production is too small too overcome the resistance.
HIT training gets some full-recruitment, which is good, but at the expense of heavy fatigue, which is bad for muscle contraction and recovery.
Max-Stimulation training gets full-recruitment (or very close) on each and every rep for multiple reps. The m-time between each rep allows the muscle to restore some lost energy reserves, putting off fatigue and allowing more total reps. More heavy reps = more full-force contractions, and hence maximal stimulation of the hypertrophy response."
